Often pipelines cannot be assembled in such a way as to be completely leak tight. In such instances, it may be necessary to apply grout at each coupling. For example, where bell and spigot coupling is used, the coupling may be quite satisfactory for joining the pipes together in line, but not satisfactory to prevent leakage at the joints either from or into the pipes. In the case of sewer pipes, in many instances, it is important to prevent leaks at these joints or couplings. Hence, in these instances grout is applied to each joint after the pipe is in place.
The materials comprising the grout are relatively expensive, and wasteful use of grout may amount to a substantial loss of money. For that reason it is important to use only the amount of grout needed, by limiting its application to the space within the coupling. Ordinarily, this has not been done. As soon as the general area of the coupling has been blocked off on both sides, the grout is applied. Sometimes this even results in making it difficult to withdraw the blocking-off equipment.
Moreover, it is important that the operator know when the joint has been properly blocked off so as to leave minimum space to be filled with grout, so that he can then apply the flow of grout. The pressure exerted against the blocking-off equipment in the space can be a good guide as to when grout can most economically be put into the joint.
Thus, it is important to provide a grout-applying system which provides for sealing off the space to be grouted, and also provides for reading the pressure exerted by the air in that space against the outer wall of the grout-applying device. Such combinations are not, so far as I am aware, known in the prior art.
Thus, it is an object of the present invention to provide method and apparatus for applying grout to pipeline joints economically.
Another object is to provide for the application of grout while sealing off on both sides the space where the grout needs to be applied, thereby preventing the waste of grout and confining it to where it is needed.
Another object is to provide for reading the pressure exerted on the outer wall of the unit through which the grout is applied and which is also accomplishing the sealing off, so that it can be known when everything is ready for the application of the grout.
Another object is to provide apparatus in which the grout can be mixed very near the point of application rather than some distance away from it in order to obtain the best characteristics for the finished product.
A further object is to provide for an apparatus for applying grout in which air pressure is used in combination with an elastic plug apparatus for sealing off the area or volume to which grout is to be applied and in which a liquid is employed to sense the pressures applied to the outer wall of the grout-applying apparatus.